Amazon's new Kindle Fire HDX 8.9 tablet may look the same on the outside as last year's model, but look under the hood and it's got a new engine, an overhauled Wi-Fi transmission system, some audio tweaks, and an updated operating system.

That's right, there's a new quad-core Snapdragon 805 processor running at 2.5 GHz, which according to Amazon delivers 70 percent faster graphics performance, along with 802.11ac MIMO Wi-Fi, said by company reps to amp up to four times the peak bandwidth.

Prices start at $379 (for the 16GB model), with the product available for pre-order now and shipping in the US in October. A 4G version is $479 and also ships in October. UK and Australian prices and availability weren't immediately available, but that converts to about £230 or AU$420 for the 16GB model, and £300 or AU$530 for the 4G.

Amazon isn't bashful about comparing the Fire HDX 8.9 to Apple's iPad Air, which is due for a processor bump of its own this fall. The impressively slim 13.2-ounce HDX 8.9 is 20 percent lighter than the iPad Air and according to Amazon, its 2,560x1,600 (339 pixels per inch) display has 30 percent more pixels than the iPad Air's Retina display.

Later this year, a new feature, Dynamic Light Control, which "changes the the white point of the display based on the ambient light of the surroundings in order to make the page of a Kindle book more closely resemble a piece of paper," will be enabled. At the launch event in New York, we got a brief demo of the feature, which showed the background of the a digital page compared to an actual printed book page in a couple of lighting conditions.

Amazon also says the HDX 8.9's speakers are twice as loud as those on the iPad Air and it's now the first tablet with Dolby Atmos, which typically requires dozens of "surround" speakers in a theater. To claim the Atmos experience can be replicated with a $379 tablet and a standard headphone is a bit of stretch (I saw a screening of "Guardians of the Galaxy" in Dolby's Atmos-enabled theater in New York City and it was pretty awesome). We got a demo and frankly I wasn't all that impressed -- it basically sounded like some faux surround. But hey, it sounds good to be the first Atmos-enabled tablet.

Amazon's step-down 2013 Fire HDX 7 won't get an upgrade at this time, but in the US Amazon has dropped the tablet's price from $229 to $199 for the 16GB model. All of Amazon's 2013 Kindle Fire tablets can be upgraded with Fire OS 4.0 and gain access to its new features.

If you're wondering whether Amazon upgraded the front- and rear-facing cameras (rear is 8MP and captures 1080p video), it didn't, but Amazon reps said some software improvements have been made to the camera. Also, battery life is still rated at "up to 12 hours of reading, surfing the Web on Wi-Fi, watching videos, and listening to music."

Same Fire HDX 8.9, just that much better

Last year's slick HDX 8.9 was a great performer and an excellent value (Editor Eric Franklin gave it high marks). Really, it was the star of Amazon's Fire lineup and in my limited time with the new version, it seemed as zippy as any tablet out there.

We'll find out just how much of a performance boost that new processor delivers and review Fire OS 4.o's new features as soon as we get our hands on a shipping unit and run it through our testing regime. But at first touch, the Fire HDX 8.9 remains an appealing choice for heavy Amazon users, particularly Prime Members, with the only big strike against it being the lack of access to the Google Play app store and no expandable memory option.